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Path: utzoo!mnetor!uunet!mcvax!cernvax!paul
From: paul@cernvax.UUCP (paul)
Newsgroups: comp.lang.ada
Subject: A Bug in Vax-Ada? (ACCVIO)
Message-ID: <585@cernvax.UUCP>
Date: 17 Dec 87 09:15:36 GMT
Reply-To: paul@cernvax.UUCP ()
Organization: CERN European Laboratory for Particle Physics, CH-1211 Geneva, Switzerland
List-Id: <comp.lang.ada>


                  <<< DISK$SYSTEM:[NOTES$LIBRARY]ADA.NOTE;1 >>>
                                    -< Ada >-
================================================================================
Note 12.0                 A bug in Vax Ada compiler...                No replies
20514::LOUBOUTIN "Sylvain R.Y. (47 27 37)"           58 lines  14-DEC-1987 18:26
--------------------------------------------------------------------------------

    A bug in Vax Ada compiler ?
    ---------------------------
     
    just have a look at that short procedure:
    
    with UNCHECKED_DEALLOCATION;
    with TEXT_IO;
    procedure G_ADA_BUG is
      type ACCESS_STRING is access STRING;
      procedure DISPOSE is new UNCHECKED_DEALLOCATION (STRING, ACCESS_STRING);
      A: ACCESS_STRING := new STRING'("Ceci est un exemple...");
      B: constant STRING := A.all;
    begin -- G_ADA_BUG
     TEXT_IO.PUT_LINE (A.all);
     TEXT_IO.PUT_LINE (B);
     DISPOSE (A);
     TEXT_IO.PUT_LINE (B);
   end G_ADA_BUG;
    
      I have compiled (with default options) it with Vax Ada V1.4-33
    running under Vax/Vms V4.5 on a Vax-8600.  
    
      The expected result is:
    
    Ceci est un exemple...
    Ceci est un exemple...
    Ceci est un exemple...
    
      But I got it:
    
Ceci est un exemple...
Ceci est un exemple...
%SYSTEM-F-ACCVIO, access violation, reason mask=00, virtual address=7FF3EA00, PC=00013FF3, PSL=0BC00000
%TRACE-F-TRACEBACK, symbolic stack dump follows
module name     routine name                     line       rel PC    abs PC
                                                           00013FF3  00013FF3
                                                           000138B0  000138B0
                                                           000138E6  000138E6
G_ADA_BUG       G_ADA_BUG                          21      000001EC  00000AD9
ADA$ELAB_G_ADA_ ADA$ELAB_G_ADA_BUG                         00000009  00000809
                                                           00000B38  00000B38
                                                           0000D1F2  0000D1F2
ADA$ELAB_G_ADA_ ADA$ELAB_G_ADA_BUG                         0000001B  0000081B
                                                           00000B13  00000B13
    
    This program behaves like if it was written like this:
    
        ...
    
      A: ACCESS_STRING := new STRING'("Ceci est un exemple...");
      B: STRING renames A.all;
    
       ...

    
    It is quit dangerous, isn'it ?
    
                                                                      SRYL